The default is now to use a *copy* of the global environment when running a
filter; this ensures better separation when `run_lua_filter` is used multiple
times. A custom environment can be specified via the optional third parameter.
This Unicode char (U+2029) is intended as a semantic separator between
paragraphs; it is cleaner and less intrusive than the pilcrow sign that
we used before. This also changes the default `sep` value used in the
`pandoc.utils.blocks_to_inlines` Lua function.
Albert Krewinkel